Camera inspection and locating

On a rainy Tuesday, Grace and Maya cleared a sewer lateral at a 1950s brick house for the third time in two years. The cable came back with fine roots and a sliver of clay. "We can keep doing this every year," Grace told the homeowner, Mr. Okafor, "or we can find out exactly what's wrong." She went back to the van for the camera. Twenty minutes later, the three of them were watching a screen as the camera head crept along the inside of the clay pipe: a cracked joint at 6 meters with a curtain of roots, a sag holding water from 9 to 11 meters, and an offset joint at 14 meters where the pipe met the city connection. Grace marked each defect on the lawn with paint after locating the camera head from above. For the first time, Mr. Okafor understood what he was paying to fix.

Drain cameras and locators changed service plumbing. Before them, plumbers diagnosed buried and hidden pipes by experience, by what came back on a cable, or by digging. Today, a plumber can see the inside of a drain, measure the distance to a defect, find its location and depth from the surface, record the inspection for the customer and the insurer, and verify that a repair was done properly. This lesson covers how cameras and locators work, how to run an inspection, how to recognize common defects, and how to report what you find.

Inspection camera systems

A drain inspection system has four main parts: a camera head, a push cable, a reel with a distance counter, and a monitor and recorder. The camera head is a small, waterproof housing with a lens, LED lights and, usually, a built-in transmitter called a sonde. The push cable is a semi-rigid fiberglass rod with wires inside that carries power and the video signal and is stiff enough to push the head through long runs and around bends. The reel stores the cable and measures how much has been pushed out, so the screen shows the distance from the entry point. The monitor displays the image and records video and still photos, often with text notes and distance overlays.

Cameras are sized for the pipe they inspect. A small camera head about 1 in across with a thin, flexible cable can travel through 1-1/2 in to 3 in lines and tight fittings such as P-traps. A mid-size head about 1-1/4 in to 1-1/2 in across with a stiffer cable inspects 3 in to 6 in building drains and laterals for distances of 200 ft or more. Larger crawler cameras on wheels inspect municipal sewers. Self-leveling heads keep the image upright as the cable rotates, which makes it much easier to tell the bottom of the pipe from the top.

Running an inspection

A good inspection starts before the camera goes in. Grace's routine was consistent.

• Clear the line first if it is blocked or full of water. A camera cannot see through standing sewage, and pushing it into a blockage risks damaging it. Flushing water through the line afterwards helps clear debris off the pipe walls.
• Choose the entry point. A cleanout close to the area of interest is best. A roof vent, a toilet flange or a fixture trap can also be used for smaller cameras.
• Zero the distance counter at the entry point and note where that is, such as the cleanout at the front wall of the basement.
• Push slowly and steadily, keeping the head centerd if possible. Stop at every joint, fitting, change in direction and defect, and record a photo or note with the distance.
• Locate the camera head from the surface at key points, such as defects, changes of direction and the property line, and mark them.
• Record the full inspection so that the customer, an insurer or the municipality can see it later.

Pushing a camera through fittings takes practice. Long-sweep fittings and wyes are easy; short-radius elbows, sanitary tees entered from the wrong direction and P-traps are hard. Pushing too hard can jam the head or damage the cable. A slight twist of the cable can help the head turn the corner. Grace never pushed a camera through a line with a cutter or debris stuck in it, and never ran it through a line that was actively draining hot water, which can damage the electronics.

Reading the picture

Interpreting what the camera shows is a skill learned by watching many inspections. A pipe in good condition has a smooth, round interior with tight joints and water running along the bottom. Common defects include the following.

Grace taught Maya to describe defects with three pieces of information: what it is, where it is (distance and position around the pipe, such as the clock position), and how bad it is. A small root intrusion at a joint is not the same as a pipe wall that has fallen in. Municipal and industry inspectors use formal coding systems for this, such as the pipeline assessment certification program used across North America, with standard defect codes and grades. Service plumbers do not usually code formally, but borrowing the idea of naming, locating and grading each defect makes reports clear and useful.

Locating: finding the camera and the pipe

The sonde in the camera head transmits a radio signal, commonly at 512 Hz, though other frequencies are used. A handheld receiver, called a locator, picks up the signal through soil, concrete and walls. Directly above the sonde, the signal pattern has a strong peak, with smaller peaks called ghost signals in front of and behind it. The locator shows the signal strength, points toward the sonde and, once you are directly above it, estimates its depth. Typical service locators can find a sonde to a depth of 15 to 20 feet.

To locate, Grace pushed the camera to the point of interest and stopped. She walked the locator along the expected path of the pipe until the signal peaked, then turned the locator and moved side to side to center over the sonde. She checked that she was over the main peak, not a ghost, by moving along the line and watching the signal rise and fall. Then she read the depth, marked the spot with paint or a flag, and wrote the distance and depth on the inspection report.

A second method locates the pipe itself rather than the camera. A line transmitter clamps onto or connects directly to a metal pipe or a tracer wire and sends a signal along it. The receiver follows the signal along the pipe's path. This works for metal water services, gas lines with tracer wire and some sewer pipes with tracer wire, but not for plastic or clay pipe without a wire. For those, the camera's sonde or a separate sonde on a push rod is used.

Locating depth matters. A plumber planning a spot repair needs to know whether the defect is 3 ft or 10 ft deep, which affects the cost, the shoring needed for the excavation and whether the work requires a permit or a dig notice. Before any digging, the location of other buried utilities must be marked through the state one-call service. In Ohio, that is OHIO811, and excavators must call 811 before digging.

# Check slope between two camera locate points (illustrative readings)
# depth is to the sonde (pipe center) measured from the surface; surface elevations from a level
points = [
    # distance from cleanout (ft), surface elevation (ft), locator depth (ft)
    (6.5, 100.00, 3.6),
    (20.0, 99.70, 5.5),
    (33.0, 99.00, 4.95),
    (46.0, 98.70, 5.25),
]
for (d1, s1, z1), (d2, s2, z2) in zip(points, points[1:]):
    invert1, invert2 = s1 - z1, s2 - z2          # pipe center elevations
    slope = (invert1 - invert2) / (d2 - d1) * 100
    flag = "OK (falls toward street)" if slope >= 1.0 else ("flat or sagging" if slope > -0.1 else "back-graded")
    print(f"{d1:4.1f} ft to {d2:4.1f} ft: slope {slope:5.2f}%  {flag}")

 6.5 ft to 20.0 ft: slope 16.30%  OK (falls toward street)
20.0 ft to 33.0 ft: slope  1.15%  OK (falls toward street)
33.0 ft to 46.0 ft: slope  4.62%  OK (falls toward street)

The program combines locator depths with surface elevations from a builder's level to estimate the slope of each segment. Locator depths have an error of a few percent, so this is a rough check, but it confirms what the camera showed: the segment between the second and third points holds water because it is nearly flat. Surface elevations must be measured, not assumed; a lawn that slopes toward the house can make a properly sloped pipe look back-graded if the surface is assumed level.

Inside buildings

Cameras are also valuable inside buildings. A camera pushed through a cleanout can show whether a kitchen line has a belly under a slab, whether a stack has corroded through, or whether a new renovation broke a drain. In condominiums and apartment buildings, cameras help sort out where a recurring blockage starts, which matters when the responsibility is split between the unit owner and the corporation or landlord. In commercial kitchens, regular camera inspections can show grease buildup before it causes a backup.

Grace also used cameras to check work. After a section of drain was replaced or lined, a camera inspection confirmed that the joints were tight, the slope was even and nothing had been left in the pipe. Many municipalities and insurers ask for post-repair video, and some new construction contracts require a camera inspection of the building sewer before the job is accepted.

Reporting to the customer

A camera inspection is only as useful as the report that comes out of it. Grace gave customers a short written summary with photos of each defect, its distance from the entry point and its location on a sketch of the property, the depth, her assessment of severity, and the repair options. She saved the video and sent the customer a link. She avoided technical jargon and explained what each defect meant in practical terms: this will keep blocking, this will get worse, this is fine for now.

Honesty matters here more than anywhere. Camera inspections have a reputation, in some places, for being used to sell unnecessary sewer replacements. Grace showed the customer the actual video, explained which defects needed action and which did not, and gave options ranging from regular maintenance cleaning to spot repair to full replacement or lining. When a defect was in the part of the lateral owned by the municipality, she said so and told the customer how to report it.